DC-to-DC converters are power converters that convert one direct current (DC) voltage into another DC voltage. While there are several DC-DC converter topologies such as low dropout (LDO), capacitive, and hysteretic, a common approach is a switch mode DC-DC converter. Switch mode DC-DC converters use a pulse width modulated (PWM) switch in series with an inductive element and change the duty cycle of the switch to determine the output voltage, and use a feedback voltage to regulate the output voltage to a desired level.
If the DC-DC converter converts an input voltage from a higher voltage to a lower output voltage, it is known as a buck converter. A typical switch mode buck converter alternatively connects the first terminal of an inductor to an input voltage or to ground to regulate the output voltage at the second terminal of the inductor to the desired level.
It is desirable to operate switch mode DC-DC converters at higher switching frequencies to reduce the size of output filters. However system efficiency goes down at higher switching frequencies due to increased switching losses associated with the metal-oxide-semiconductor field effect transistors (MOSFETs) used to switch current through the inductor. These switching losses are especially undesirable in low-voltage battery powered equipment because the extra switching losses decrease battery life.
The use of the same reference symbols in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.